The Neoshield project for Near-Earth object impact threat mitigation

Every day Earth is hit by around 100 tonnes of cosmic material, most of it comes in the form of dust or small rocks, which burn up as meteors in the atmosphere. Sometimes, however, larger objects, asteroids or comets, enter the Earth’s atmosphere and then even relatively small objects can cause considerable damage. The object that exploded over the Russian city of Chelyabinsk in February 2013 had a diameter of only 17–20 m, yet it produced a blast wave that damaged buildings and injured some 1500 people. It entered the Earth’s atmosphere with a velocity of 65 000 km/h and, due to the frictional heating and stresses caused by compression of the air, it exploded at an altitude of some 25 km releasing an energy 30 times that of the Hiroshima bomb. The potentially devastating effects on Earth of a collision with a large asteroid or comet are now well recognized by scientists and policy makers. So the question is now, can we protect our civilization from the next major impact? NEOShield, a project funded by the European Commission’ Seventh Framework Programme, brought together an international team of 13 partner organizations from 6 countries to address the global issue of near-­‐Earth object (NEO) impact prevention. The project ran from 2012 to mid 2015, after which the NEOShield-­‐2 project funded by the European Commission’ H2020 Programme is continuing the research until fall 2017. The purpose of the projects is to carry out detailed analysis of realistic options for preventing a potentially catastrophic impact of a NEO on Earth. While a mitigation test mission is beyond the financial scope of the current project, the NEOShield technical partners, with the support of the science team, aim to provide detailed designs of appropriate test-­‐missions for the 3 most feasible mitigation concepts: kinetic impactor, gravity tractor, and blast deflection, so that it will be possible to quickly develop an actual test mission at a later stage. Project partners are also carrying out research into the mitigation-­‐relevant physical properties of NEOs, including observations of near-­‐Earth asteroids, analysis of available observational data, laboratory experiments on asteroid analogue materials, and modelling and computer simulations. The aim of the scientific work is to facilitate predictions of the outcome of deflection attempts using different techniques on a variety of NEO types

Metallic Asteroids in the IRAS Minor Planet Survey - a NEOShield Study

Studies of the compositions of asteroids, especially their metal content, are relevant not only to investigations of their nature, but also to estimations of their potential to wreak devastation on impacting the Earth. In this respect it is informative to compare the airburst of a stony object, such as the Tunguska event, which destroyed a forest but left no crater, with the impact of a similarly sized metallic object, which produced the 1.2 km diameter Barringer Crater in Arizona. In view of the evident link between metal content and the near-Earth asteroid thermal model (NEATM; Harris 1998) fitting parameter, eta, which carries information on thermal inertia (Harris and Drube, 2014; see abstract submitted to this conference), we are carrying out a re-analysis of Infrared Astronomical Satellite (IRAS) data (Tedesco et al., 2002) with NEATM to further explore the dependence of eta and thermal inertia on metal content. In addition to calculating best-fit values of eta, we are calculating the angle between the spin vector and the solar direction, theta, for all IRAS sightings of each asteroid for which a spin vector is available. The eta values of objects with high thermal inertia and moderate to high spin rates should depend strongly on theta, whereas those with low thermal inertia and/or low spin rates should not. By studying the relationships between theta and eta, we aim to further explore the potential of the results of Harris and Drube (2014) and provide insight into relationships between asteroid thermal properties, taxonomic type, albedo, spin rate, etc. We will present the first results of our work and provide a demonstration of its potential. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 282703 (NEOShield Project). Harris, A. W., 1998, Icarus, 131, 291. Harris, A. W. and Drube, L, 2014, Ap. J. Letters, 785, L4 Tedesco, E. F. et al, 2002, Astron. J., 123, 1056

Asteroid Thermal Inertia Estimates from Remote Infrared Observations: The Effects of Surface Roughness and Rotation Rate

The thermal inertia of an asteroid's surface can provide insight into regolith properties, such as the presence of a layer of fine dust, the density and thermal conductivity of a rocky surface, and, together with other observational data, mineralogy. Knowledge of the surface characteristics of asteroids is important for planetary defense initiatives and the extraction of resources ("asteroid mining"). A simple means of estimating asteroid thermal inertia has been proposed by Harris & Drube, which is suitable for application to large sets of thermal-infrared observational data, such as those obtained by infrared space telescopes. We compare results from the Harris-Drube estimator with recently published values of asteroid thermal inertia from detailed thermophysical modeling, and provide an explanation in terms of reduced surface roughness for some discrepant results. Smooth surfaces covered in fine dust may provide an explanation for the unexpectedly low values of thermal inertia derived from thermophysical modeling for some slowly rotating main-belt asteroids (MBAs). In the case of near-Earth objects (NEOs) we show that results from the estimator are in good agreement with those from thermophysical modeling, with just a few exceptions. We discuss the special cases of the NEOs (101955) Bennu, (162173) Ryugu, and (29075) 1950 DA in the context of results from our estimator. Given the data requirements and complexity of thermophysical modeling, data-analysis tools based on relatively simple concepts can play an important role in allowing "quick-look" assessment of thermal-infrared data of asteroids, especially NEOs.Comment: 24 pages, 9 figures, Accepted Manuscript, Ap

Interface Engineering to Create a Strong Spin Filter Contact to Silicon

Integrating epitaxial and ferromagnetic Europium Oxide (EuO) directly on silicon is a perfect route to enrich silicon nanotechnology with spin filter functionality. To date, the inherent chemical reactivity between EuO and Si has prevented a heteroepitaxial integration without significant contaminations of the interface with Eu silicides and Si oxides. We present a solution to this long-standing problem by applying two complementary passivation techniques for the reactive EuO/Si interface: ($i$) an $in\:situ$ hydrogen-Si $(001)$ passivation and ($ii$) the application of oxygen-protective Eu monolayers --- without using any additional buffer layers. By careful chemical depth profiling of the oxide-semiconductor interface via hard x-ray photoemission spectroscopy, we show how to systematically minimize both Eu silicide and Si oxide formation to the sub-monolayer regime --- and how to ultimately interface-engineer chemically clean, heteroepitaxial and ferromagnetic EuO/Si $(001)$ in order to create a strong spin filter contact to silicon.Comment: 11 pages of scientific paper, 10 high-resolution color figures. Supplemental information on the thermodynamic problem available (PDF). High-resolution abstract graphic available (PNG). Original research (2016

Dealing with Uncertainties in Asteroid Deflection Demonstration Missions: NEOTwIST

Deflection missions to near-Earth asteroids will encounter non-negligible uncertainties in the physical and orbital parameters of the target object. In order to reliably assess future impact threat mitigation operations such uncertainties have to be quantified and incorporated into the mission design. The implementation of deflection demonstration missions offers the great opportunity to test our current understanding of deflection relevant uncertainties and their consequences, e.g., regarding kinetic impacts on asteroid surfaces. In this contribution, we discuss the role of uncertainties in the NEOTwIST asteroid deflection demonstration concept, a low-cost kinetic impactor design elaborated in the framework of the NEOShield project. The aim of NEOTwIST is to change the spin state of a known and well characterized near-Earth object, in this case the asteroid (25143) Itokawa. Fast events such as the production of the impact crater and ejecta are studied via cube-sat chasers and a flyby vehicle. Long term changes, for instance, in the asteroid's spin and orbit, can be assessed using ground based observations. We find that such a mission can indeed provide valuable constraints on mitigation relevant parameters. Furthermore, the here proposed kinetic impact scenarios can be implemented within the next two decades without threatening Earth's safety.Comment: Accepted for publication in the proceedings of the IAUS 318 - Asteroids: New Observations, New Models, held at the IAU General Assembly in Honolulu, Hawaii, USA 201

Тренинг толерантности : учеб.-метод. пособие

A versatile experimental setup is presented for both x‐ray standing waves (XSW) and x‐ray photoemission spectroscopy (XPS) studies in an energy range up to 7 keV. The compact apparatus operates under ultrahigh vacuum and includes in situ sample preparation and characterization techniques. For the XSW scans the incident photon energy is tuned through the Bragg reflection from the sample for ΘB ≊ 90° while measuring the intensity and energy distributions of both the emitted electrons and fluorescence radiation simultaneously. Alternatively, desorbing positive ions can be analyzed as a function of the standing wave phase shift using a time‐of‐flight spectrometer. In addition, energy dependent high‐energy XPS measurements with medium overall energy resolution (ΔE=1.5 eV at 3 keV) can be performed. Selected results obtained at the focused EXAFS II beamline of HASYLAB are shown

Temperature dependent Eu 3d-4f X-ray Absorption and Resonant Photoemission Study of the Valence Transition in EuNi2(Si0.2Ge0.8)2EuNi_2(Si_{0.2}Ge_{0.8})_2

We study the mixed valence transition ($T$$_{v}$ $\sim$80 K) in EuNi$_{2}$(Si$_{0.2}$Ge$_{0.8}$)$_{2}$ using Eu 3$d-4f$ X-ray absorption spectroscopy (XAS) and resonant photoemission spectroscopy (RESPES). The Eu$^{2+}$ and Eu$^{3+}$ main peaks show a giant resonance and the spectral features match very well with atomic multiplet calculations. The spectra show dramatic temperature ($T$)-dependent changes over large energies ($\sim$10 eV) in RESPES and XAS. The observed non-integral mean valencies of $\sim$2.35 $\pm$ 0.03 ($T$ = 120 K) and $\sim$2.70 $\pm$ 0.03 ($T$ = 40 K) indicate homogeneous mixed valence above and below $T$$_{v}$. The redistribution between Eu$^{2+}$$4f^7$+$[spd]^0$ and Eu$^{3+}$$4f^6$+$[spd]^1$ states is attributed to a hybridization change coupled to a Kondo-like volume collapse.Comment: 4 pages, 3 figure

Raman and fluorescence contributions to resonant inelastic soft x-ray scattering on LaAlO3_3/SrTiO3_3 heterostructures

We present a detailed study of the Ti 3$d$ carriers at the interface of LaAlO$_3$/SrTiO$_3$ heterostructures by high-resolution resonant inelastic soft x-ray scattering (RIXS), with special focus on the roles of overlayer thickness and oxygen vacancies. Our measurements show the existence of interfacial Ti 3$d$ electrons already below the critical thickness for conductivity and an increase of the total interface charge up to a LaAlO$_3$ overlayer thickness of 6 unit cells before it levels out. By comparing stoichiometric and oxygen deficient samples we observe strong Ti 3$d$ charge carrier doping by oxygen vacancies. The RIXS data combined with photoelectron spectroscopy and transport measurements indicate the simultaneous presence of localized and itinerant charge carriers. However, it is demonstrated that the relative amount of localized and itinerant Ti $3d$ electrons in the ground state cannot be deduced from the relative intensities of the Raman and fluorescence peaks in excitation energy dependent RIXS measurements, in contrast to previous interpretations. Rather, we attribute the observation of either the Raman or the fluorescence signal to the spatial extension of the intermediate state reached in the RIXS excitation process.Comment: 9 pages, 6 figure